ZBrush beginner - something like a xy fill plane appeared after pressing some shortcut

2visible

As I was trying to familiarize myself with the tools (following some tutorial from the zbrush website) i accidentally pressed some combination of keys and suddenly my screen was filled with this gray colour, clipping the model on the xy plane.

is this some 2.5 D feature? how can i get rid of that plane?
thank you!

Marvin Mann

Have you tried Layer -> Clear at the top?

2visible

i did now and, thank you so much, it worked!